REGENSBURG, Germany — Pope Benedict XVI weighed in Tuesday on the sensitive issue of rapport between Islam and the West: He said that violence, embodied in the Muslim idea of "jihad," or holy war, is contrary to reason and God's plan, while the West was so beholden to reason that Islam could not understand it.

Nonetheless, in a complex treatise delivered at the university here where he once taught, he suggested reason as a common ground for a "genuine dialogue of cultures and religions so urgently needed today."

In all, the speech seemed to reflect the Vatican's struggle over how to confront Islam and terrorism, as the 79-year-old pope pursues what is often considered a more provocative, hard-nosed and skeptical approach to Islam than his predecessor, John Paul II.

As such, it distilled many of Benedict's long-standing concerns, about the crisis of faith among Christians and about Islam and its relationship to violence.

And he used language open to interpretations that could inflame Muslims, at a time of high tension among religions and three months before he makes a trip to Turkey.

He began his speech, which ran over half an hour, by quoting a 14th-century Byzantine emperor, Manuel II Paleologus, in a conversation with a "learned Persian" on Christianity and Islam —"and the truth of both."

"Show me just what Muhammad brought that was new, and there you will find things only evil and inhuman, such as his command to spread by the sword by the faith he preached," the pope quoted the emperor, in a speech to 1,500 students and faculty.

He went on to say that violent conversion to Islam was contrary to reason and thus "contrary to God's nature."

But the section on Islam made up just three paragraphs of the speech, and he devoted the rest to a long examination of how Western science and philosophy had divorced themselves from faith — leading to the secularization of European society that is at the heart of Benedict's worries.

This, he said, has closed off the West from a full understanding of reality, making it also impossible to talk with cultures for whom faith is fundamental.

"The world's profoundly religious cultures see this exclusion from the divine, from the universality of reason as an attack on their most profound convictions," he said. "A reason which is deaf to the divine and which relegates religion into the realm of subcultures is incapable of entering into the dialogue of cultures."